BRITISH AVONIAN CONODONT FAUNAS 147 
anterior and posterior edges and feebly convex to flat lateral faces. They are 
separated by a single similar denticle, widely spaced between them but only about 
one fifth to one sixth of the length of the larger denticles they separate. The 
posterior end of the lateral bar is marked by one such denticle which extends 
downwards to form the bluntly triangular distal end of the bar. At the anterior end 
of the lateral bar there are 2 to 3 smaller denticles of this general kind. The inner 
aboral surface of the posterior bar is marked by a variably developed flange, which 
although laterally persistent is irregular in the extent to which it invades the lateral 
face of the unit. It tends to do this to a rather small degree and its greatest aboral 
extension is under the posterior third of the bar. 
The posterior bar is very small in comparison with the lateral bar and is strongly 
recurved, so that in oral view it makes an angle of about 30° with the lateral bar. It 
is also sharply convex and seems to bear rather small denticles although in the present 
specimens it is broken. The largest of these small denticles, occurs at its junction 
with the lateral bar. It tends to decrease in depth distally at its junction with the 
lateral bar, just anterior to the bluntly spatulate termination of the latter. In outer 
lateral view the outer lateral bar is flat and the outer lateral surface of the denticles 
are also markedly flat ; only a few of them show any degree of convexity. There is no 
sign in outer lateral view of the scar-like presence of the inner callus. In aboral view 
a thin slit occurs along the length of the lateral blade and is also developed, though in 
much reduced width, below the posterior bar. 
REMARKS. The specimens referred to this species show some variation in the 
development of the callus on the inner lateral face and also in the depth of the lateral 
bar, which tends in some specimens to be deeper in its medial third than its distal 
third. 
Magnilaterella contraria sp. nov. 
Plate 23, figs. 8a—c, 18a—c 
1941 Ligonodina ? sp. Branson & Mehl: 171, Pl. 5, fig. 11. 
1963 New Gen. et sp. Rexroad & Collinson : 21, Pl. 3, fig. 2. 
DERIVATION OF NAME. With reference to the morphology. 
DiaGnosis. Magnilaterella characterized by very delicate and slender construc- 
tion. Short lateral bar bearing three isolated and recurved denticles, the largest 
being the middle : bar very shallow decreasing in height posteriorly, and making an 
obtuse angle with posterior bar. 
MATERIAL. 3 specimens : Holotype X 553, Paratype X 517 (both figured). 
TYPE LOCALITY AND HORIZON. North Crop. Sample 3D 23. 
Rance. North Crop 3D 23. 
DEscRIPTION. The lateral bar is short and more or less straight in a vertical plane 
but is strongly recurved, so that its basal surface is continuously concave in lateral 
view. It is of very slender construction and bears only 3 or 4 denticles, the two in 
the medial part being much larger than those at either end. The denticles are 
